Vision 2009 Tries to Understand the Workings of the Human Eye. This collection discusses the human eye. Its workings and features.
Inner Workings of the Eye
At a certain place in the brains, at height of the cerebral cortex, all perceptions of the rods and cones are caught and converted.
Both optic nerves join there. And then something peculiar happens. The brains constantly correct the incoming information and they add some fantasy at it.
At a certain place in the brains, at height of the cerebral cortex, all perceptions of the rods and cones are caught and converted. Both optic nerves join there. And then something peculiar happens. The brains constantly correct the incoming information and they add some fantasy at it. Therefore you don't see what you really see, but what the brains “translate”. In fact looking is one big puzzle of our brains. If you look at something, you overlook the whole surface. The brains get lots of informations and make it into one .
The visual centre has a connection with other centres of the brains. The information is compared, much quicker than the fastest computer could do, with all what's already been filed in the memory. In that way the brains try to make the incoming information “useful”. Whatever you see, is always coloured by the things you've seen and experienced before.
Central in seeing is the yellow spot. Only at that spot we can see sharply. With the rest of the retina we look unsharply. Therefore the yellow spot is called the central visual centre; the rest is the peripheral visual centre.
The nerves of the outside of the eye-ball can turn the eyes. In that way we are able to focus our eyes. To focus means: move the head and eyes in such a way that the image enters the yellow spot. So we are able to look sharper.
Still the peripheral visual centre is very important. Through it you are able to orientate and it allows us to observe enough elements from our surroundings. Thank to your peripherical visual centre you are able to see the sidewards movement of a pedestrian at the other side of the street.
We can compare the working of the eye with a camera. Both the eye and the camera can be considered as the diaphragm. The retina functions as a sensitive “film” on which the image from outside is pictured.
Just like a photo- or film camera the eye needs light in the first place. When a ray of light reaches the eye it will bend by the system of the lenses. Therefore the ray of light falls on the retina. The image which is formed through that is upside-down and is reduced. The image only gets its meaning when via the optic nerve it reaches the visual centre of the brains. Here the images of both eyes are combined and the interpretation takes place.
Intensive and detailed watching happens through the yellow spot. But if you would like to spot a weak star at night, you better focus right next to it.Then the image of that star won't be much longer at the yellow spot but next to it on the retina, where there are more rods. Because those rods are more sensitive than cones, such a star can be looked at much better.
Iris and pupil
The iris is coloured and that colouring depends on the pigmentation. When there is less pigmentation the iris is blue, when there is much pigmentation the iris is brown. The opening in the centre is the pupil and through the pupil the eye regulates the ray of light. The pupil will narrow at much light and wider at less light. Both pupils change at the same time, in a reflex. Not only the light influences the pupils. Reduction also takes place when one takes a close look at objects, while the pupils are widening if the see something touching or exciting.
The eye has a diameter of two and a halve centimetre. It exists of three big parts:
• the eye-wall: the outside of the eye, which works as a camera;
• the vitreous humour: a clear, gelatinous fluid which gives the eye its form
• the optic nerve: the cable that connects the eye to the brains.
The eye-wall too exists of three basic parts:
• a tough outer layer: the sclera
• a middle layer with many blood vessels and pigment: the choroid
• an inner layer with sensitive cells: the retina
The iris determines the colour of the eyes. It can be compared to the diaphragm of a camera. In the centre of the iris is an opening: the pupil. Orbicular muscles make the opening wider or smaller. When there is much light, the pupil becomes more narrow. At twilight or darkness the pupil widens. So the pupil is an opening, although it seems to be black. That colour exists because the eye doesn't reflect the light that enters.
Behind the iris is the lens. It is kept at its place by very small fibres. The lens surely is transparant. It has the shape of a globoid. The inner eye muscles can change the globoid of the lens and that way sharpen the incoming image.
Iris and lens divide the eye into the foremost and the rear chamber of the eye.
The retina has got two types of cells. The rods are especially on the side of the retina. They are only sensitive to light and darkness. The cones are more in the centre. They are more sensitive to colours. People have about one million rods and seven million cones.
Exactly behind the pupil is the most sensitive spot of the retina: the yellow spot. There are only cones. At that spot in the eye we can see the colours very well and the sight is quite clearly.
From the rods and cones the nerve-fibres leave. They join at the end of the eye, in the big optic nerve. At that spot there aren't any rods or cones. There the retina is insensitive to light and darkness. That's why that spot is called the blind spot.
The eyes are protected in a naturel way. They are safely in sockets to stand rough handling. Besides they are extra protected by the lids which can close in a reflex when danger threatens. One winks the lids about ten to fifthteen times a minute. In a smokey area, in stress or in concentration it happens even more. The importance of winking is that every time a little tear-water is spread over the eye. Tear-water protects the eyeball from drying and kills damaging bacterium. The whiskers protect the eye against dirt, small insects and sunlight, while the brows protect the eyes from rain or sweat.
First the rays of light are bent by the surface of the cornea and eventually by the natural lens. The cornea is the outer layer of the eye. It is transparant and has a spherical shape. The rays of light which enters the eye are bent by the cornea.
The natural lens, which is flexible and can accommodate of shape, is behind the pupil and it converts the fine-tune of the rays. A strong bending of the lens is for instance needed for reading. Between the 40 th and 50 th year of life the lens will become less flexible and old person's far-sightness starts. Later on, the lens can become turbid and tough. This is a matter of cataract.
Inner Workings of the Eye
At a certain place in the brains, at height of the cerebral cortex, all perceptions of the rods and cones are caught and converted.
Both optic nerves join there. And then something peculiar happens. The brains constantly correct the incoming information and they add some fantasy at it.
To the brains
At a certain place in the brains, at height of the cerebral cortex, all perceptions of the rods and cones are caught and converted. Both optic nerves join there. And then something peculiar happens. The brains constantly correct the incoming information and they add some fantasy at it. Therefore you don't see what you really see, but what the brains “translate”. In fact looking is one big puzzle of our brains. If you look at something, you overlook the whole surface. The brains get lots of informations and make it into one .
The visual centre has a connection with other centres of the brains. The information is compared, much quicker than the fastest computer could do, with all what's already been filed in the memory. In that way the brains try to make the incoming information “useful”. Whatever you see, is always coloured by the things you've seen and experienced before.
Central and peripheral
Central in seeing is the yellow spot. Only at that spot we can see sharply. With the rest of the retina we look unsharply. Therefore the yellow spot is called the central visual centre; the rest is the peripheral visual centre.
The nerves of the outside of the eye-ball can turn the eyes. In that way we are able to focus our eyes. To focus means: move the head and eyes in such a way that the image enters the yellow spot. So we are able to look sharper.
Still the peripheral visual centre is very important. Through it you are able to orientate and it allows us to observe enough elements from our surroundings. Thank to your peripherical visual centre you are able to see the sidewards movement of a pedestrian at the other side of the street.
The Workings of the Eye
Just like a photo- or film camera the eye needs light in the first place. When a ray of light reaches the eye it will bend by the system of the lenses.We can compare the working of the eye with a camera. Both the eye and the camera can be considered as the diaphragm. The retina functions as a sensitive “film” on which the image from outside is pictured.
The Working Of the Eye
We can compare the working of the eye with a camera. Both the eye and the camera can be considered as the diaphragm. The retina functions as a sensitive “film” on which the image from outside is pictured.Just like a photo- or film camera the eye needs light in the first place. When a ray of light reaches the eye it will bend by the system of the lenses. Therefore the ray of light falls on the retina. The image which is formed through that is upside-down and is reduced. The image only gets its meaning when via the optic nerve it reaches the visual centre of the brains. Here the images of both eyes are combined and the interpretation takes place.
Retina
An important part of seeing so happens on the retina which contains sensitive cells. When such a cell is moved by a ray of light an electricstimulus exists which is passed on through the optic nerve to the brains. There are two types of sensitive cells: cones and rods.The cones receive strong light and can distinguish colours. The rods react on weak light, through which one is able to see in the twilight or at night. On the retina, right behind the pupil, there is a place with a high concentration of cones which is called the yellow spot. From the yellow spot to the edges of the eye the cones reduce and the rods increase.Intensive and detailed watching happens through the yellow spot. But if you would like to spot a weak star at night, you better focus right next to it.Then the image of that star won't be much longer at the yellow spot but next to it on the retina, where there are more rods. Because those rods are more sensitive than cones, such a star can be looked at much better.
Iris and pupil
The iris is coloured and that colouring depends on the pigmentation. When there is less pigmentation the iris is blue, when there is much pigmentation the iris is brown. The opening in the centre is the pupil and through the pupil the eye regulates the ray of light. The pupil will narrow at much light and wider at less light. Both pupils change at the same time, in a reflex. Not only the light influences the pupils. Reduction also takes place when one takes a close look at objects, while the pupils are widening if the see something touching or exciting. The Human Eye
The eye provides vision in humans.
"The only thing worse than being blind is having sight but no vision"The Eye
The eye has a diameter of two and a halve centimetre. It exists of three big parts:
• the eye-wall: the outside of the eye, which works as a camera;
• the vitreous humour: a clear, gelatinous fluid which gives the eye its form
• the optic nerve: the cable that connects the eye to the brains.
The eye-wall too exists of three basic parts:
• a tough outer layer: the sclera
• a middle layer with many blood vessels and pigment: the choroid
• an inner layer with sensitive cells: the retina
The Outer Layer of The Eye-Wall
The tough sclera is what we call the white part of the eye. It is a white, transparant membrane which protects and strengthens the eye. The tough sclera changes into the transparant cornea, which is covered with a protective conjunctiva. If compared to a camera the cornea is the window through which the rays of light enter.The Middle Layer
The middle layer of the eye-wall is the choroid. It consists of many blood vessels. They tranfer the nutrients to the right place and regulates the temperature. The choroid first enters the corpus ciliare and then the iris.The iris determines the colour of the eyes. It can be compared to the diaphragm of a camera. In the centre of the iris is an opening: the pupil. Orbicular muscles make the opening wider or smaller. When there is much light, the pupil becomes more narrow. At twilight or darkness the pupil widens. So the pupil is an opening, although it seems to be black. That colour exists because the eye doesn't reflect the light that enters.
Behind the iris is the lens. It is kept at its place by very small fibres. The lens surely is transparant. It has the shape of a globoid. The inner eye muscles can change the globoid of the lens and that way sharpen the incoming image.
Iris and lens divide the eye into the foremost and the rear chamber of the eye.
The Inner Layer
The inner layer of the eye-wall is the retina. If you compare it again with a camera, the retina is the shield on which the images are projected. Millions of cells are on it, which are sensible to the light. Everything they sense, they transmit to the optic nerve.The retina has got two types of cells. The rods are especially on the side of the retina. They are only sensitive to light and darkness. The cones are more in the centre. They are more sensitive to colours. People have about one million rods and seven million cones.
Exactly behind the pupil is the most sensitive spot of the retina: the yellow spot. There are only cones. At that spot in the eye we can see the colours very well and the sight is quite clearly.
From the rods and cones the nerve-fibres leave. They join at the end of the eye, in the big optic nerve. At that spot there aren't any rods or cones. There the retina is insensitive to light and darkness. That's why that spot is called the blind spot.
Protection
The eyes are protected in a naturel way. They are safely in sockets to stand rough handling. Besides they are extra protected by the lids which can close in a reflex when danger threatens. One winks the lids about ten to fifthteen times a minute. In a smokey area, in stress or in concentration it happens even more. The importance of winking is that every time a little tear-water is spread over the eye. Tear-water protects the eyeball from drying and kills damaging bacterium. The whiskers protect the eye against dirt, small insects and sunlight, while the brows protect the eyes from rain or sweat. Aging
The eye converts rays of light into electrical signals. The brains convert these signals and therefore we are able to see.To get a clear image we have to bend tha rays of light so that they join together exactly on the retina in the rear of the eye.First the rays of light are bent by the surface of the cornea and eventually by the natural lens. The cornea is the outer layer of the eye. It is transparant and has a spherical shape. The rays of light which enters the eye are bent by the cornea.
The natural lens, which is flexible and can accommodate of shape, is behind the pupil and it converts the fine-tune of the rays. A strong bending of the lens is for instance needed for reading. Between the 40 th and 50 th year of life the lens will become less flexible and old person's far-sightness starts. Later on, the lens can become turbid and tough. This is a matter of cataract.
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